A rapid thermal processing apparatus heats a substrate at a high rate using infrared light emitted from heating lamps for thermal processing. At this time, various attempts, for example, horizontal rotation of the substrate, have been made to achieve uniform heating of the substrate. However, problems caused by arrangement of heating lamps make it difficult to achieve uniform heating of the substrate, thereby causing a minute temperature gradient on the substrate. Such a temperature gradient provides an increasingly disadvantageous influence on reliability and yield of devices with increasing circuit integration.
FIG. 1 is a bottom view illustrating a conventional concentric arrangement of heating lamps viewed from a lower surface of the heater block 10, that is, from a side of the heater block opposite to a heating target such as a substrate. Referring to FIG. 1, the heater block 10 is provided with a plurality of heating lamps 20. FIG. 2 illustrates a T-shaped heating lamp 28 provided as the heating lamp 20 of FIG. 1. For differentiation, the T-shaped heating lamp is denoted by a different reference numeral than a general heating lamp. As shown in FIG. 2, the T-shaped heating lamp 28 has a T-shape in side view, and a straight rod shape in a bottom view of the heating lamp. In the side view of the heating lamp, an upward protrusion of the T-shaped heating lamp 10 is fitted into the heater block 10 when mounting the T-shaped heating lamp 10 on the heater block 10. Accordingly, when the heater block 10 is viewed from the lower surface thereof, with the T-shaped heating lamp 28 fitted into the heater block 10 as shown in FIG. 1, the T-shaped heating lamp 28 has a straight rod shape. Conventionally, such T-shaped heating lamps 28 are concentrically arranged on the heater block.
However, the concentric arrangement of the heating lamps forms a void in the form of a straight line 21 and a concentric circle 22 as indicated by a dashed dot line, so that a substrate (not shown) is not uniformly heated due to generation of heat overlapping sections and voids between the heat overlapping sections even when the substrate is rotated, thereby causing a minute temperature gradient on the substrate.
FIG. 3 is a bottom view of another conventional concentric arrangement of heating lamps. Even in the concentric arrangement shown in FIG. 3, it is difficult to prevent creation of voids in the form of a straight line 21 and a concentric circle 22.
As described above, the conventional concentric arrangement of the heating lamps inevitably incurs the temperature gradient on the substrate even in the case of horizontally rotating the substrate, and requires a complex structure for sector allocated temperature control, in which the heater block is divided into sectors such that power applied to the heating lamps is adjusted according to the sectors, in order to eliminate the temperature gradient on the substrate.